1) Technical Field
The subject invention relates to a beverage filling machine having an adjustable vent tube.
2) Description of the Prior Art
Filling mechanisms used for filling containers, such as cans, jars, or bottles, with a beverage, such as beer or soft drinks, are well known in the art. The conventional filling mechanisms feed the containers into a star wheel conveyor which individually positions each container on a rotating turntable below a valve assembly of an individual filling machine. The container moves into sealing engagement with the valve assembly by either moving the container upwardly or by lowering the valve assembly. The filling machines are known in the art as counter pressure filling machines as is discussed below. There may be as many as 120 individual filling machines disposed circumferentially around the turntable. The filling machines typically include a support housing having an inner fluid chamber or ring bowl disposed above the valve assembly. The ring bowl is usually annular and contains the liquid or beverage for filling the containers and has a space above the liquid for a pressurized inert gas such as carbon dioxide or nitrogen. This space above the liquid is known as the headspace. A common storage tank or reservoir feeds each individual ring bowl with the liquid and gas.
In the typical filling operation, the container, which is sealed against the valve assembly, is initially purged with the inert gas from the ring bowl for a predetermined time in order to flush air and other impurities from the container. A vent tube is introduced into the container to accomplish this an other operations. The liquid is filled into the container from the ring bowl while the gas from the container vents through the vent tube into the headspace. The liquid will at least partially rise into the vent tube during the filling of the container. The gas pressure in the container and the ring bowl are equalized when filling begins. This is what is known as counter pressure, which allows the liquid to flow into the container solely under the influence of gravity. After the container is filled to a desired level, the vent tube rises out of the container. Finally, gas is released from the headspace of the container to the atmosphere by an process commonly known as "snifting".
The beverage filling industry continuously strives for machinery and methods which facilitate rapid, economical, efficient, and sterile filling of containers. As discussed above, methods and apparatuses for filling containers with carbonated liquids have evolved into counter pressure filling machines. The prior art devices utilize complicated mechanical or pneumatic mechanisms for adjusting the height of the vent tube during the filling operation.
Examples of such devices are shown in U.S. Pat. No. 3,595,280 to Fissel and U.S. Pat. No. 3,633,635 to Kaiser. These known devices can be expensive and difficult to maintain.
Further, such mechanical or pneumatic devices could significantly jeopardize the sterile environment of the filling machines. In particular, the known prior art devices utilize a number of seals which separate the inner working components of the filling machine, which include the vent tube, with the atmosphere. The pressures exerted against the seals can be significant. Hence, after repeated use, the seals are subject to failure which reduces the operating life of the filling valves and effects the integrity of the entire filling machine.
Accordingly, there is a need for a vent tube adjustment mechanism which is of a relatively simple design and does not jeopardize the sterile environment of the filling machines. The adjustment mechanism preferably eliminates the seals which are subject to the counteracting pressures of the filling machines, thereby reducing the likelihood of a failure.